An optical communication technique in which an electric signal is converted into an optical signal to transmit information is characterized by enabling to raise communication speed more and transmit larger-capacity data than an electric communication. Recently, such characteristics of the optical communication technique attract attention, and a newly constructed building is designed in advance so that an optical fiber can be laid at the time of construction in many cases while an existing building is also provided with an optical fiber in many cases.
As a method for distributing an optical fiber, various wiring methods such as under-carpet wiring, exposed wiring, and concealed wiring are conventionally known. Recently, the concealed wiring is carried out in many cases from a viewpoint of enabling preservation of appearance even with distribution of the optical fiber. The concealed wiring is a wiring method for providing a pipe under a floor, in a ceiling, in a sidewall of a building, and the like in advance at the time of construction of the building and inserting the optical fiber into the provided pipe. In a case where the optical fiber is laid in an existing building, a pipe cannot be buried in a wall and the like, and thus a pipe is provided in an inconspicuous position of the building in advance before the optical fiber is distributed, and the optical fiber is inserted into this pipe.
Conventionally, a method of inserting the optical fiber provided at a tip end with an optical fiber connector into the pipe has been general. However, the optical fiber connector has a complicated structure provided with various members such as a latch to be used when the connector is connected to an adapter and when connection to the adapter is cancelled and easily gets stuck when the optical fiber is inserted into the pipe, which may cause disconnection of the optical fiber or breakage of the optical fiber connector. Also, when the disconnection of the optical fiber or the breakage of the optical fiber connector occurs, the optical fiber that has been inserted into the pipe has to be pulled, a new optical fiber has to be connected, or the optical fiber connector has to be replaced, and thereafter the optical fiber has to be inserted into the pipe again, which brings about poor operating efficiencies.
Also, the pipe is provided in a bent or curved state in some cases depending on a structure of the building and ways to arrange or lay the pipe. Especially in a case where the pipe is provided in this manner, the optical fiber connector easily gets stuck, which easily causes the aforementioned disconnection of the optical fiber or breakage of the optical fiber connector.
Various methods for solving such problems have been considered conventionally. For example, in an optical connector described in Patent Literature 1, a cap formed in a shape that does not cause the cap to easily get stuck in a pipe is attached to the optical connector to insert an optical fiber into the pipe, and the optical connector is adapted to enable the optical fiber to be inserted into the pipe smoothly and enable to reduce disconnection of the optical fiber or breakage of the optical connector.
Also, conventionally known is an optical fiber in which a surface of a covering material is subjected to a special process so as to reduce resistance between the optical fiber and an inner circumferential surface of a pipe to facilitate insertion into the pipe. This optical fiber is adapted to attach and fix an optical connector to the optical fiber after the optical fiber is inserted into the pipe.
Further, conventionally known as a method for inserting an optical fiber into a pipe is a method for inserting an optical fiber into a pipe while supplying gas such as compressed air in the pipe in an equal direction to a direction in which the optical fiber is inserted. By this method as well, the optical fiber can be inserted into the pipe easily, which can reduce disconnection of the optical fiber or breakage of an optical connector.